dm: add statistics support
Support the collection of I/O statistics on user-defined regions of
a DM device. If no regions are defined no statistics are collected so
there isn't any performance impact. Only bio-based DM devices are
currently supported.
Each user-defined region specifies a starting sector, length and step.
Individual statistics will be collected for each step-sized area within
the range specified.
The I/O statistics counters for each step-sized area of a region are
in the same format as /sys/block/*/stat or /proc/diskstats but extra
counters (12 and 13) are provided: total time spent reading and
writing in milliseconds. All these counters may be accessed by sending
the @stats_print message to the appropriate DM device via dmsetup.
The creation of DM statistics will allocate memory via kmalloc or
fallback to using vmalloc space. At most, 1/4 of the overall system
memory may be allocated by DM statistics. The admin can see how much
memory is used by reading
/sys/module/dm_mod/parameters/stats_current_allocated_bytes
See Documentation/device-mapper/statistics.txt for more details.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index e151d4c..653073d 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -10,6 +10,7 @@
#include <linux/bio.h>
#include <linux/blkdev.h>
+#include <linux/math64.h>
#include <linux/ratelimit.h>
struct dm_dev;
@@ -550,6 +551,14 @@
#define DM_MAPIO_REMAPPED 1
#define DM_MAPIO_REQUEUE DM_ENDIO_REQUEUE
+#define dm_sector_div64(x, y)( \
+{ \
+ u64 _res; \
+ (x) = div64_u64_rem(x, y, &_res); \
+ _res; \
+} \
+)
+
/*
* Ceiling(n / sz)
*/